Re: LuaJIT FFI callbacks

[Florian Weimer <fw@...>]

* Mike Pall:

> tl;dr: Just pass a Lua function to a C function taking a callback
> argument and the FFI will do all the magic in the background.

I'm trying to figure out what made this feat suddenly possible.  I was
under the impression that it wouldn't be possible introduce, say,
allocations into traces which were deemed allocation-free before.

By the way, you could probably use stubs of the form

  CALL vm_ffi_callback
  RET

and derive the slot and the address of the state pointer from the
return address on the stack within vm_ffi_callback.  This would allow
you to squeeze a few more stubs into that memory area.